Factor out verify_storage.h
Factor out verify_exec.h
Introduce SyntaxCheck, PromiseKept and Repair for verify_exec

This is a proof of concept for splitting the traditional Verify function
for modules. It splits Verify into 3 stages, syntax checking (evaluation stage),
status checking (whether the promise needs repair), and Repair. Repair returns an
ActionResult, specifying the outcome of attempting to repair the promise.

The end goal is to have all modules take a struct with callbacks to these functions,
enabling pluginification and a step towards introducing isolated evaluation state
(by effectively removing cfPS from lower levels).

Additionally, a GetLockName function is needed for each promise type, but this
may be reconsidered in the future (when we get around to reconsider locking).
Merge pull request #296 from sigurdteigen/cleanup/split-verify

Introduce SyntaxCheck, PromiseKept and Repair for verify_exec
et rid of MINGW, use __MINGW32__ instead (Redmine #2018)
Implement automatic discovery and bootstrap for cf-agent.

cf-agent discovers policy servers using Avahi implementation of Zeroconf protocol
at runtime using dlopen.

If a single hub is discovered cf-agent will automaticaly bootstrap to it.

If there's more than one hub discovered cf-agent will print a message listing
available hub and ask user to manualy bootstrap to a proper IP address using
--bootstrap --policy-server <right IP address> command line option.

To use automatic bootstrap --bootstrap/-B command line option is required without
specifying the IP address.
Implement generation of Avahi configuration file.

Add new command line option to cf-serverd -A. cf-serverd executed
with this option will generate Avahi configuration file in
/etc/avahi/services and restart avahi-daemon to make policy server
discoverable over the network.
Register atexit function to close loaded library.
Move include of atexit.h to findhub.c .
Check if avahi is installed on the machine while running configure.
Fix wrong atexit function name.
Enable -A option for cf-serverd only if avahi is installed on host.
Use generic linked list for storing information about found hosts.